1. Field of the Invention
The present invention generally relates to a vertical transistor of a semiconductor device and a method for forming the same, and more specifically, to a vertical transistor of a semiconductor device and a method for forming the same wherein a pair of vertical gates comprising a gate polysilicon layer and a gate metal layer are disposed on sidewalls of a silicon fin to improve driving current capability of the semiconductor device.
2. Description of the Related Art
Generally, one of the most important parameters in fabricating a transistor is a threshold voltage. The threshold voltage is a variable depending on a thickness of a gate oxide film, a channel doping concentration, an oxide charge, and a material used for gate.
As the size of semiconductor device is decreased, phenomena inconsistent with a theory occur. One of the inconsistent phenomenons at hand is a short channel effect (“SCE”) that occurs due to decrease in a gate channel length.
As integration density of the semiconductor device is increased, a transistor having a high operation speed and a low operation voltage is required. However, it becomes difficult to form the transistor having a high operation speed and a low operation voltage by using conventional methods due to the SCE.
Moreover, the SCE causes a Hot Carrier Effect (“HCE”) Hot carrier refers to a carrier or an electron/hole having a high energy due to acceleration when an electric field is applied.
The hot carrier is one of several factors that have significant effect on the characteristics of semiconductor device. The hot carrier causes a Drain Induced Barrier Lowering (“DIBL”) and a Gate Induced Barrier Lowering (“GIBL”), which deteriorate an electric characteristic of the semiconductor device.
In accordance with the above-described conventional transistor of a semiconductor device, problems such as SCE, HCE, DIBL and GIDL occur due to decrease in the size of the semiconductor device. As a result, the electric characteristics and reliability of the semiconductor device are deteriorated.